International Business Machines Corporation

Other

Peter P Sorokin

Rodney T Hodgson

Michael M Loy

Donald Stimson Bethune

John R Lankard

Daniel R Grischkowsky

James Glownia

A novel practicable type of gaseous optical gain medium for efficiently generating intense, highly monochromatic, continuous-wave (CW) or pulsed, coherent light beams is disclosed. Gain results from nonlinear optical pumping of a gas of &#x39b;-type 'three-level' atoms, coherently phased ('dressed') via application to the medium of two monochromatic laser beams tuned to the resonance frequencies &#x3c9;and &#x3c9;'. Nonlinear optical pumping of the &#x201c;dressed-atom&#x201d; gas is accomplished through the combined action of two separate physical processes: (1) A low pressure gaseous discharge, occurring continuously within the vessel containing the gain medium, produces intense narrow-band fluorescence at &#x3c9;and &#x3c9;&#x2032;through the process of electron impact excitation (EE). (2) Via a specific form of the nonlinear photonic process of stimulated hyper-Raman scattering (SHRS), photons comprised by the narrow-band fluorescence generated in (1) are efficiently converted to photons comprised by the propagating coherent light beams at &#x3c9;and &#x3c9;&#x2032;, thus effecting amplification of the latter.

Discharge-pumped 'dressed-atom' coherent light amplifier and generators

A coherent tunable narrow band IR source in the vicinity of 16 .mu.m is achieved by four-wave parametric mixing in parahydrogen. A pair of colinear laser beams, one from a narrow band CO.sub.2 laser, and a second from a multiline laser with output of wave number significantly below 14,400 cm..sup.-1, is focused in a parahydrogen containing cell. The multi-line laser beam drives a Raman process in the cell. The narrow band CO.sub.2 input beam mixes with this driver beam and the Stokes wave resulting from the Raman process to produce a 16 .mu.m output beam. Tuning of the CO.sub.2 laser allows tuning of the 16 .mu.m radiation emitted by the parahydrogen cell.

Tunable 16-micron coherent source including parahydrogen Raman

Apparatus for producing tunable intense coherent radiation at approximately 628 cm..sup.-1 with a line width less than 0.1 cm..sup.-1. The apparatus includes an optical cavity containing a vapor cell and pumping means including at least one optical pumping source for directing energy at the cavity. In one embodiment the cavity encloses a material capable of stimulated emission in response to said pumping. The material has at least three atomic energy levels with at least a first and second atomic energy level separated by a particular energy quantum approximately equal to 628 cm.sup.-1 ; a transition from said first to said second atomic energy level favored over all other possible transitions from said first atomic energy level; said third atomic energy level, from which atoms can be pumped to said first atomic energy level in response to said pumping means. While this is consistent with classical laser operation the apparatus disclosed herein can also be used for stimulated Raman scattering. Tunability is achieved by tuning the pumping sources in the case of stimulated Raman scattering, or with the aid of the Zeeman or Stark effects for classical laser operation. Typical materials are potassium or strontium vapors. Several pumping arrangements are also disclosed.

Apparatus for producing tunable intense coherent radiation in the

An intense broadband continuum light pulse of uniform spectral intensity and short time duration is generated. This continuum pulse is then downconverted in frequency to a region of interest, preferably in the infrared region, by applying it as a pump pulse to a molecular or atomic vapor so as to induce stimulated Raman scattering. The resulting Raman Stokes pulse surprisingly tends to have the same spectral bandwidth, intensity uniformity and time duration as the pump continuum pulse. The downconverted continuum pulse (the Raman Stokes pulse) is then used to probe a sample. The sample converts the uniform spectral intensity distribution of the probe pulse into a nonuniform spectral intensity distribution which contains the absorption spectrum of the sample. This spectrum pulse has the same spectral bandwidth and time duration as the Raman Stokes pulse and is finally upconverted in frequency to a region where the spectrum pulse can be conveniently recorded. This is done with a four-wave Raman mixing process in an alkali metal vapor. The vapor is simultaneously pumped with the spectrum pulse and with a second pumping light pulse (or beam) having a frequency in the vicinity of a suitable resonance line of the vapor so as to induce SERS. In the alkali metal vapor, the resulting Raman Stokes pulse and spectrum pulse beat together with the second pumping light pulse to produce an upconverted pulse at a higher frequency band, which surprisingly also tends to have the same spectral bandwidth, intensity distribution (spectrum) and time duration as the spectrum pulse. The upconverted pulse is then recorded either photographically or photoelectrically with conventional spectrographic apparatus.

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Ossining, NY, United States of America

Peter P Sorokin